Hydraulic hammers are used on work sites to break up large, hard objects before the objects can be moved away. Hydraulic hammers may be mounted to machines including, but not limited to backhoes, excavators, tractors, skid steer loaders or other machines, as will be apparent to those skilled in the art. Hydraulic hammers may also be hand-held. Typically, the hammer is powered by a hydraulic pressure source although pneumatic pressure sources are known. A typical hydraulic hammer includes a pressurized liquid circuit that is in communication with a reciprocating piston that may engage a tool or bit that engages the work surface. More specifically, during a work or power stroke, high pressure liquid is applied to at least one shoulder of the piston that is disposed within a cylinder. Pressure on the shoulder drives the piston in a downward or forward direction. The piston then strikes the bit, which is driven in the downward or forward direction thereby causing the bit to strike the work surface (e.g., the rock, concrete, asphalt or other hard object to be broken up). During a return stroke, liquid pressure is applied to at least one other shoulder of the piston in order to return or retract the piston and the bit back to their original positions.
In addition to a liquid circuit that drives the hammer as discussed above, hydraulic hammers may also include a gas circuit for absorbing, reducing or minimizing vibrations and noise from the liquid circuit. Hydraulic hammers may also include an accumulator that couples the liquid circuit to the gas circuit. Specifically, the vibration/noise in the liquid circuit may be caused by pressure variations in the liquid circuit. Such pressure variations in the liquid circuit may be caused by pressure pulsations or pulsating flow of the liquid in the liquid circuit. An accumulator for a hydraulic hammer may typically include a base and a cover that form a vessel. The vessel may be divided by a deformable partition member, such as a diaphragm. The diaphragm divides the vessel into a gas chamber that is in communication with the gas circuit and a liquid chamber that is in communication with the liquid circuit. The term diaphragm, as used herein, is intended to encompass any flexible barrier, partition, wall or member that can divide a vessel, such as an accumulator, into two isolated chambers as described above. The gas chamber is typically filled with nitrogen or another gas, which is pressurized. In response to a pressure increase in the liquid circuit, liquid may be discharged from the liquid circuit to the liquid chamber, thereby causing the diaphragm to be biased towards the gas chamber. Conversely, in response to a pressure decrease in the liquid circuit, liquid may be discharged from the liquid chamber to the liquid circuit, thereby causing the diaphragm to be biased towards the liquid chamber. Accumulators are designed to effectively absorb or accommodate the pulsating flow of the liquid in the circuit and consequently reduce or alleviate vibrations and noises caused by the pulsating flow.
However, current accumulators typically include a base that must allow liquid to pass through the base freely, but which also must be rigid. The base must not have large holes or gaps; otherwise the diaphragm could be extruded or damaged by the base if the diaphragm is pressed against the large holes or gaps with significant pressure. Currently, typical accumulator bases have large amounts of small holes or perforations, sometimes in excess of 1000. A base of this type is expensive to manufacture, in part because of the many holes and the need to deburr and clean the holes after they are formed in the base.
Accordingly, accumulator designs with improved base structures are needed that both effectively reduce vibration and noise caused by pulsating flow in a pressurized liquid circuit and which are inexpensive and easy to manufacture.